The 66-year-old Ibrahim, who has previously denied any connection with Shah, told the Straits Times that the pilot is in fact related to his son-in-law.

"I am not denying that he [Zaharie] is related to one of my in-laws and that I have met him on several occasions," Ibrahim said.

"In fact, he is a close friend of Rasiah Sivarasa [a leading figure in Ibrahim's PKR party], as we said before."

Ibrahim had previously said "I don't recollect the name" of Shah, however he claimed he had "seen him at party meetings", suggesting the pilot was politically active - something which has been widely denied.

'No political fanatic'

It is claimed that Shah attended Ibrahim's latest trial, at which he was jailed for five years for sodomy, just seven hours before embarking on the MH370 flight.

The trial, which reversed Ibrahim's previous acquittal of sodomy charges, has been condemned by human rights groups, many of whom believe the charges are political in nature.

Police sources say Captain Shah was a political activist and fear that the court decision left him profoundly upset.

The PKR party has also admitted that Shah previously campaigned for Ibrahim's PKR party.

However a PKR spokesperson has rubbished media reports which alleged that Shah was a "political fanatic" who hijacked the flight out of contempt for Malaysia's rulers.

PKR communications director Fahmi Fadzil said the reports were "wild allegations" and the paper in question, the Daily Mail, "is a sensationalist tabloid known for cooking up stories".

One of the party's senior lawmakers, Sivarasa Rasiah, did admit that Shah became a PKR member in January 2013 - but insisted "this is irrelevant to the case."

'A decent man'

Ibrahim has defended Shah as a "decent" man after media coverage placed Shah as the main suspect in the investigation of the missing airliner.

"Is it a crime for anyone to be a member of [PKR]? To me it is an attempt to deflect the government's incompetence," Ibrahim told AFP.

"I of course did not take the news reports [about Shah] seriously but I am speaking out because I sympathise with the pilot and his family.

"The mysterious disappearance of MH370 reflects not only an incompetent regime ruling the country but an irresponsible government."

Ibrahim, who has already served six years in prison, many of them in solitary confinement, advocates opposition to Malaysia's ruling United Malays National Organisation (UMNO) through elections, rather than 'fanatical' terrorism.